1. Field of the Invention
The present invention relates to display devices. More particularly, the present invention relates to display devices having pixels comprising red, green, and blue sub-pixels.
2. Discussion of the Related Art
Generally, cathode ray tubes (CRTs) are commonly used as display devices. Flat panel displays, having a lightweight, compact construction, and which consume low amounts of power (e.g., liquid crystal displays (LCDs), plasma display panels (PDPs), field emission displays, and electro-luminescence displays (ELDs)) are also commonly used. Contrary to other types of display devices, LCDs are non-luminous display devices in that they cannot display images without some light source (e.g., ambient light or a backlight).
FIG. 1 illustrates a related art LCD device.
Referring to FIG. 1, the related art LCD device 100 generally includes a timing controlling portion 130, a gray-level generation portion 120, a gate driving portion 140, a data driving portion 150, and a display portion 160.
The timing controlling portion 130 supplies R (red), G (green), and B (blue) data signals to the data driving portion 150, and a plurality of control signals to gate and data driving portions 140 and 150, respectively, enabling the LCD device 100 to display images.
The gray-level generating portion 120 generates “i”-number of gray-level voltages “V1˜Vi” corresponding to “i”-number of gray-levels. Thus, where the supplied R, G, and B data signals each have 8 bits, the gray-level generating portion 120 generates 28 gray-level voltages “V1˜V256”.
The gate driving portion 140 outputs gate signals to gate lines 145 and the data driving portion 150 outputs data signals to data lines 155.
The display portion 160 includes a plurality of pixels arranged in a matrix pattern. Each pixel includes R, G, and B sub-pixels that display red, green, and blue colors, respectively. Each sub-pixel includes a thin film transistor “T”, a liquid crystal capacitor “CLC”, and a storage capacitor “CST”.
A gate electrode of each thin film transistor “T” is connected to a corresponding gate line 145, a source electrode of each thin film transistor “T” is connected to a corresponding data line 155, and a drain electrode of each thin film transistor “T” is connected to a first electrode of a corresponding liquid crystal capacitor “CLC”. A second electrode of each liquid crystal capacitor “CLC” is connected to a common electrode. A first electrode of each storage capacitor “CST” is connected to a drain electrode of a corresponding thin film transistor “T” and a second electrode of each storage capacitor “CST” is connected to a previous one of the gate lines 145.
To drive the above-described related art LCD device 100, one of a plurality of gate lines 145 is selected during a frame and a gate-ON signal is supplied to each thin film transistor “T” via the selected gate line 145. Supplied with the gate-ON signal, each thin film transistor “T” is provided in an ON-state and a channel of each thin film transistor “T” is provided in an open state.
While the channel of each thin film transistor “T” is provided in the open state, the data driving portion 150 supplies R, G, and B data signals to respective ones of the R, G, and B sub-pixels connected to the selected gate line 145. Accordingly, R, G, and B data signals supplied to R, G, and B sub-pixels are charged within the liquid crystal capacitor “CLC” and the storage capacitor “CST” of each sub-pixel.
Next, an immediately succeeding gate line 145 is selected, and the thin film transistors “T” connected with the previously selected gate line 145 is provided in an OFF-state. However, the R, G, and B data signals, charged within the liquid crystal capacitor “CLC” and the storage capacitor “CST” of the sub-pixels connected to the previously selected gate line 145 remain charged therein until a next frame. By repeating the operation described above, the display portion 160 displays images.
FIG. 2 illustrates a gamma curve of a related art liquid crystal display device having a gamma value “γ” of 2.2.
Referring to FIG. 2, the gamma curves of white, red, green, and blue colors are equal. Therefore, the related art liquid crystal display device expresses a white color at the same brightness level as it would express red, green, and blue colors when a data signal corresponding to the white color has a same gray-level of data signals corresponding to the red, green, and blue colors. As a result, the display region 160 displays pictures at a reduced contrast ratio, making it difficult to display distinct images.
FIG. 3 illustrates a picture displayed by a related art liquid crystal display device.
Referring to FIG. 3, a difference in brightness levels to which white, red, green, and blue colors is minimal. As a result, the images of the helicopter and surrounding bushes are not distinct.